1. Field of the Invention
This invention relates in general to the field of resource management, and more particularly to an apparatus and method for coordinating the use of certain resources such that a peak demand of those resources is optimized.
2. Description of the Related Art
The problem with resources such as electrical power, water, fossil fuels, and their derivatives (e.g., natural gas) is that the generation and consumption of a resource both vary with respect to time. Further, the delivery and transport infrastructure limits instantaneous matching of generation and consumption. They are limited in supply and the demand for this limited supply is constantly fluctuating. As anyone who has participated in a rolling blackout will concur, the times are more and more frequent when resource consumers are forced to face the realities of limited resource supply.
Most notably, the electrical power generation and distribution community has begun to take proactive measures to protect limited instantaneous supplies of electrical power by imposing a demand charge on consumers in addition to their monthly usage charge. Heretofore, consumers merely paid for the total amount of power that they consumed over a billing period. Today most energy suppliers are not only charging customers for the total amount of electricity they have consumed over the billing period, but they are additionally charging them for their peak demand, that is the greatest amount of energy that they use during a measured period, typically on the order of minutes.
For example, consider a factory owner whose building includes 20 air conditioners, each consuming 10 KW when turned on. If they are all on at the same time, then the peak demand for that period is 200 KW. Not only does the energy supplier have to provide for instantaneous generation of this power in conjunction with loads exhibited by its other consumers, but the distribution network that supplies this peak power must be sized such that it delivers 200 KW.
So it is acceptable today that high peak demand consumers are required to pay a surcharge to offset the costs of peak energy generation and distribution. And the notion of peak demand charges, while presently being levied only to commercial electricity consumers and to selected residential consumers, is applicable to all residential consumers and consumers of other limited generation and distribution resources as well. Water and natural gas are prime examples of resources that will someday exhibit demand charges.
But consider in the facility example above that it is not time or comfort critical to run every air conditioning unit in the building at once. Run times can be staggered, perhaps, to mitigate peak demand. And this technique is what is presently employed in the industry to lower peak demand. There are very simple ways to stagger run times, and there are very complicated mechanisms that are employed to lower peak demand, but they all utilize variations of what is known in the art as deferral.
Stated simply, deferral means that some devices have to wait to run while other, perhaps higher priority, devices are allowed to run. Another form of deferral is to reduce the duty cycle (i.e., the percentage of a device cycle that a device is on) of one or more devices in order to share the reduction in peak demand desired. What this means in the air conditioning example above is that some folks are going to be very uncomfortable while waiting for their turn to run, or that everyone in the facility is going to be mildly uncomfortable. And as one skilled in the art will appreciate, there is a zone of comfort beyond which productivity falls.
Virtually every system of resource consuming devices exhibits a margin of acceptable operation (“comfort zone” in the air conditioning example above) around which operation of the device in terms of start time, duration, and duty cycle can be deferred. But the present inventors have observed that present day techniques for controlling peak demand all involve delaying (“deferring”) the start times and durations of devices and decreasing the duty cycles, thus in many instances causing local environments to operate outside of their acceptable operational margins. It is either too hot, too cold, not enough water, the motors are not running long enough to get the job done, and etc.
Accordingly, what is needed is an apparatus and method for managing peak demand of a resource that considers acceptable operational margins in determining when and how long individual devices in a system will run.
What is also needed is a technique for scheduling run times for devices in a controlled system that is capable of advancing the start times and durations of those devices, and that is capable of increasing the duty cycles associated therewith in order to reduce demand while concurrently maintaining operation within acceptable operational margins.
What is additionally needed is a mechanism for modeling and coordinating the operation of a plurality of devices in order to reduce peak demand of a resource, where both advancement and deferral are employed effectively to reduce demand and retain acceptable operational performance.
What is moreover needed is a demand coordination apparatus and method that employs adaptive modeling of local environments and anticipatory scheduling of run times in order to reduce peak demand while maintaining acceptable operation.
Furthermore, what is needed is a demand coordination mechanism that will perform reliably and deterministically in the presence of periodic network disruptions.